In a letter to Singh, she said families of the fishermen, hailing from Ramanathapuram, Nagapattinam and Kaniyakumari districts, had recently submitted a petition to her, stating that the fishermen are the sole breadwinners of the family.

These fishermen, engaged as contract labourers by a private company based in Saudi Arabia, had accidentally ventured into Iranian waters and were taken into custody in December 2012.

"Without access to legal aid, they were convicted by an Iranian court to undergo six months imprisonment and pay a fine of USD 5,750 each," she said.

Even after having served their term, they continued to languish in jail due to lack of resources to pay the fine, she said.

"What is more shocking is that they have not even been able to contact the Indian Embassy. No effort has been made by the Embassy to establish contact with them or provide legal assistance to them or to put any pressure on the employer Company which engaged them to secure their release by settling the fine amount", she said.

"I am bringing this matter to your notice seeking your immediate and personal intervention to instruct the Embassy of India in Tehran to take effective legal steps to secure the release of these poor fishermen, who have undergone the period of imprisonment, but continue to languish in jail for want of means to pay the fine amount", she said.

She also urged Singh to instruct the Indian Embassy in Saudi Arabia to take steps to settle the fine amounts ensuring the release of the fishermen.